1. Field of the Invention
The present invention relates to a field emission electrode that emits electrons due to field emissions, a manufacturing method thereof, and a manufacturing apparatus thereof.
2. Description of Related Art
A field emission electrode is capable of emitting cold electrons in a vacuum as a result of the application of a strong field to an emitter and is noted as an electron emission element that can replace a hot cathode. Various researches are being made to bring about a lower threshold field intensity and achieving stability and uniformity of emission current.
Structures such as those utilizing carbon film such as carbon nanotubes as a field emission electrode are well known.
It is well known that, typically, with field emission electrodes, when polar molecular gas such as water vapor is absorbed at a surface of an electron emission site (taken to be “water molecules” hereafter because most of the residual gas within a vacuum chamber evacuated from atmospheric pressure can be considered to be that which desorbs absorbed water molecules within the chamber), a work function of an emitter surface is reduced and an electron emission characteristic is improved (a high number of electron emissions at a lower field intensity). It is also well known that an absorption state to the electron emission element for the water molecules changes according to the degree of vacuum and that the electron emissions are dependent on the degree of vacuum.
This changing of the characteristics by absorbing of molecules enables the electron emission characteristics to be improved on the one hand (larger number of electron emissions with a lower field intensity), while on the other hand degrading the degree of vacuum because molecules that have adhered to electron emission sites are desorbed in a vacuum with electron beam irradiation. Degradation of the degree of vacuum means an increase in ionized molecules and ions due to the electron beam irradiation that then collide with the electron emission element due to the electrical field, thus causing the electron emission element to be degraded. The degradation is also subject to positive feedback as a result of a large amount of gas being desorbed from the emitter surface as a result of the collisions. If the degree of vacuum degrades by more than a certain extent, the ion collisions will promote spark discharges. This will cause substantial damage to the electron emission element and the surrounding electrode structure. It is therefore typical for products utilizing field electron emission elements to be provided with a process for removing gas from the electron emission element and the electrode structure driving the electron emission element (even in the case of water molecules provided to improve the electron emission characteristics). Many patent applications have been made with regards to such methods.
Heating processing in an evacuated vacuum state referred to as baking and processing referred to as aging disclosed in Unexamined Japanese Patent Application KOKAI Publication No. 2000-243291 taking degassing as an object are well known as methods for degassing electron emission elements and their anodes.
This invention is taking the lead in forming electron emission films including nanodiamond fine particles of a particle diameter smaller than 1 μm using plasma CVD techniques. However, with plasma CVD, it is difficult to make active species density uniform across the entire surface of a substrate where a nanodiamond fine particle layer is formed and bias occurs in the electron emission characteristics of the electron emission film according to the position of the substrate. When bias in the electron emission characteristics is made uniform using normal aging means (removal by combustion of low field electron emission sites in the electron emission film) using techniques to make the bias in the electron emission characteristics uniform, characteristics of portions where the electron emission characteristics are weak are made uniform and the total quantity of electron emissions for the emitter is substantially reduced.
In order to resolve the situation described above, the present invention is advantageous in providing a method of manufacturing a field emission electrode having comparatively uniform electron emission density, a field emission electrode, and a manufacturing apparatus.